Because even though they like to stick "Pro" in product names, Apple mostly targets consumers, and few normal people need 10GbE. In other words, they don't think they'd make enough money from it.
Many of us pro uses the macbook pro m1 max but it's to bad that they dont make a 10gbe fo that. mac mini, mac pro etc has 10GbE so.... But yes maybe to little market but I don't 1GbE is to slow for most of us that useing it for video producktion etc